Synucleinopathies, also known as Lewy body diseases (LBDs), are characterized by deposition of intracellular protein aggregates that are microscopically visible as Lewy bodies (LBs) and/or Lewy neurites, where the protein alpha-synuclein is the major component (Jellinger, Mov Disord. 2012 January; 27(1):8-30; McKeith et al., Neurology (1996) 47:1113-24). Synucleinopathies include Parkinson's disease (PD) (including idiopathic and inherited forms of Parkinson's disease) and Diffuse Lewy Body (DLB) disease (also known as Dementia with Lewy Bodies (DLB), Lewy body variant of Alzheimer's disease (LBV), Combined Alzheimer's and Parkinson disease (CAPD), pure autonomic failure (PAF) and multiple system atrophy (MSA; e.g., Olivopontocerebellar Atrophy, Striatonigral Degeneration and Shy-Drager Syndrome)). Synucleinopathies frequently have degeneration of the dopaminergic nigrostriatal system, responsible for the core motor deficits in Parkinsonism (rigidity, bradykinesia, resting tremor), but there is also widespread occurrence of Lewy bodies and dystrophic Lewy neurites in the central, peripheral and autonomic nervous system and brain regions and other organs associated with non-motor dysfunctions, such as dementia and autonomic nervous system deficits. Several of the non-motor signs and symptoms are thought to precede motor symptoms in Parkinson's disease and other synucleinopathies. Such early signs include, for example, REM sleep behaviour disorder (RBD) and loss of smell and constipation (Mahowald et al., Neurology (2010) 75:488-489). Synucleinopathies continue to be a common cause for movement disorders and cognitive deterioration in the aging population (Galasko et al., Arch. Neurol. (1994) 51:888-95).
Alpha-synuclein is a member of a family of proteins including beta- and gamma-synuclein and synoretin. Alpha-synuclein is expressed in the normal state associated with synapses and is believed to play a role in regulating synaptic vesicle release and thereby affecting neural communication, plasticity, learning and memory.
Several studies have implicated alpha-synuclein with a central role in PD pathogenesis. The protein can aggregate to form intracellular insoluble fibrils in pathological conditions. For example, synuclein accumulates in LBs (Spillantini et al., Nature (1997) 388:839-40; Takeda et al., J. Pathol. (1998) 152:367-72; Wakabayashi et al., Neurosci. Lett. (1997) 239:45-8). Mutations in the alpha-synuclein gene as well as duplications and triplications of the gene co-segregate with rare familial forms of parkinsonism (Kruger et al., Nature Gen. (1998) 18:106-8; Polymeropoulos, et al., Science (1997) 276:2045-7). An important finding has been that alpha-synuclein can be secreted into the extracellular fluid and be present in plasma and cerebrospinal fluid (CSF). Several studies, for example by Pacheco et al. (2015) and others (Pacheco et al J Neurochem. 2015 March; 132(6):731-4; Conway et al., Proc Natl Acad Sci USA (2000) 97:571-576; Voiles et al., J. Biochem. 42:7871-7878, 2003) have suggested that extracellular-synuclein plays a pathogenic role in the brain. They demonstrated that extracellular alpha-synuclein oligomers possesses neurotoxicity toward brain neuronal plasma membranes. Another intriguing hypothesis based on the data of synuclein secretion is that a prion-like spread of alpha-synuclein underlies the progression of Parkinson's disease and other synucleinopathies (Lee et al. 2014, Nat Rev Neurol. 2014 February; 10(2):92-8; Hansen and Li 2012, Trends Mol Med. 2012 May; 18(5):248-55). These findings have given rise to a hope that extracellular-synuclein could be targeted by immunotherapy (Vekrellis et al. 2011, Lancet Neurol. 2011 November; 10(11):1015-25).
Naturally occurring alpha-synuclein auto-antibodies have been shown to be present in both PD patients and healthy controls (Smith et al. 2012, PLoS One. 2012; 7(12):e52285; Maetzler et al. 2014, PLoS One. 2014 Feb. 21; 9(2):e88604, Papachroni et al. 2007 J Neurochem. 2007 May; 101(3):749-56 and Woulfe et al. 2002, Neurology. 2002 May 14; 58(9):1435-6), sometimes increased levels of auto-antibodies to alpha-synuclein in PD (Gruden et al. 2011, J Neuroimmunol. 2011 April; 233(1-2):221-7, Gruden et al. 2012, Neuroimmunomodulation. 2012; 19(6):334-42 and Yanamandra 2011, PLoS One. 2011 Apr. 25; 6(4):e18513) or decreased auto-antibodies to alpha-synuclein in PD patients compared to healthy controls have been reported (Besong-Agbo et al 2013, Neurology. 2013 Jan. 8; 80(2):169-75). The possibility that circulating anti-alpha-synuclein autoantibodies may serve a protective role with respect to alpha-synuclein aggregation was suggested very early on after finding of the auto-antibodies (Woulfe et al. 2002, Neurology. 2002 May 14; 58(9):1435-6).
Over expression of alpha-synuclein in transgenic mice mimics some pathological aspects of Lewy body disease. Several different transgenic lines of mice over-expressing alpha-synuclein have been generated in the last ten years (described in reviews: Koehler et al 2014, PLoS One. 2013 May 31; 8(5):e64649; Fleming and Chesselet, 2006, Behav Pharmacol. 2006 September; 17(5-6):383-91; Springer and Kahle 2006, Curr Neurol Neurosci Rep. 2006 September; 6(5):432-6). Mouse lines with Thy-1 and PDGF-beta promoters develop motor deficits and cognitive deficits and have been used to demonstrate a neuroprotective effect of antibodies directed against alpha-synuclein in vivo. However, none of the transgenic lines have robust degeneration of dopaminergic neurons, and often the motor phenotypes are driven by expression in motor neurons, which do not normally degenerate in Parkinson's disease. Therefore, it is not clear if positive outcome of a potential disease modifying treatment is mediated through effects on dopaminergic neurons or other central nervous system neurons.
One robust finding in the transgenic mouse models has been that chronic overexpression of human alpha-synuclein impairs synaptic function. Using studies in both in vitro and in vivo systems it was shown that overexpression of wild-type (wt) human alpha-synuclein impaired synaptic transmission in hippocampus (Nemani et al. 2010, Neuron. 2010 Jan. 14; 65(1):66-79; Paumier et al. 2013, PLoS One. 2013 Aug. 1; 8(8):e70274). This was shown in the CA1 region of the hippocampus where both studies found reduced basal synaptic transmission. The mechanism behind this was assumed to be intracellular accumulation of alpha-synuclein leading to dysfunctional synaptic release. However, the recent findings about secretion of alpha-synuclein into extracellular space in synapses and the toxic effects of alpha-synuclein oligomers on synapse function opens for the possibility of a role of extracellular alpha-synuclein in synaptic dysfunction, and as such for the ability of therapeutic antibodies to rescue the deficit.
The use of viral vectors to over-express alpha-synuclein represents an important way to model PD in rodents because this approach produces a relative fast progressive degeneration of nigrostriatal neurons, a feature not yet reproduced by genetic mutations in mice or rats (Kirik and Bjorklund, 2003, Trends Neurosci. 2003 July; 26(7):386-92). Furthermore, viral gene delivery revealed the ability of wt alpha-synuclein to induce nigrostriatal pathology (Kirik et al. 2002, J Neurosci. 2002 Apr. 1; 22(7):2780-91), a finding in agreement with evidence in familial forms of PD with alpha-synuclein duplications and triplications (Lee and Trojanowski, 2006, Neuron. 2006 Oct. 5; 52(1):33-8). In one study, it has been shown that a a pool of goat antibodies against the alpha-synuclein N-terminal protected against dopaminergic cell death and ameliorated behavioural deficits in a AAV-alpha-synuclein based rat model of Parkinson's disease (Shahaduzzaman et al 2015, PLoS One. 2015 Feb. 6; 10(2):e0116841).
Prion like spreading of alpha-synuclein pathology has recently been shown to develop alpha-synuclein pathology and also develop dopaminergic cell death (Luk et al. 2012, Science. 2012 Nov. 16; 338(6109):949-53). This model has been used to show that alpha-synuclein antibodies are able to ameliorate the pathology (Tran et al. 2014, Cell Rep. 2014 Jun. 26; 7(6):2054-65). In this model antibody treatment was able to reduce accumulation of phosphorylated alpha-synuclein in several brain regions—including dopaminergic neurons in substantia nigra, and reduce development of motor deficit.
In addition to mutations, alternative splicing of the alpha-synuclein gene and posttranslational modifications of the protein, such as phosphorylation, ubiquitination, nitration, and truncation can create alpha-synuclein protein forms that have enhanced capacity to form aggregated and/or toxic forms of alpha-synuclein (Beyer and Ariza, Mol Neurobiol. 2013 April; 47(2):509-24). However, the precise pathological species of alpha-synuclein remains unknown. Various misfolded/aggregated/secreted species ranging from oligomers to fibrils, and different post-translational modifications have been associated with toxicity but there is no consensus on which is most important, if indeed there even is a single toxic species.
Overall the accumulation of alpha-synuclein with similar morphological and neurological alterations in animal models as diverse as humans, mice, and flies suggests that this molecule is central in the pathogenesis of Lewy body diseases.
Several different antibodies to alpha-synuclein have been shown to have therapeutic effect in preclinical animal models. Both an antibody targeting an epitope involving alpha-synuclein residues 91-99 and antibodies targeting an epitope that involves alpha-synuclein residues 118-126 have been shown to have an effect on motor and cognitive deficits in transgenic mice (Games et al. 2014, J Neurosci. 2014 Jul. 9; 34(28):9441-54). The most advanced of these antibodies is a humanized antibody based on the mouse monoclonal antibody 9E4, which targets an epitope that involves alpha-synuclein residues 118-126, and which is now in clinical trials in phase I. A C-terminal antibody 274 which targets an epitope that involves alpha-synuclein residues 120-140 (Bae et al. 2012, J Neurosci. 2012 Sep. 26; 32(39):13454-69) was also shown to have an effect in a preclinical model on spreading of the pathology from cell to cell. In addition to these, antibodies targeting conformational species such as oligomers and fibrils of alpha-synuclein have been shown to be able to at least reduce the levels of these presumably toxic alpha-synuclein species (Lindström et al. 2014, Neurobiol Dis. 2014 September; 69:134-43 and Spencer et al. 2014, Mol Ther. 2014 October; 22(10):1753-67). These conformational antibodies that lower alpha-synuclein oligomer levels in vivo, such as mab47 were also shown to target epitopes in the C-terminus of alpha-synuclein, from amino acid 121-125 (US20120308572). Other conformational, fibril and oligomer specific antibodies also target C-terminal sequences (Vaikath et al. Neurobiol Dis. 2015; 79:81-99).
As the toxic form of alpha-synuclein is unknown, a therapeutic antibody should be ideally able to bind to most of the alpha-synuclein species that are formed by alternative splicing or posttranslational modifications, such as truncations, as well as oligomeric and fibrillary forms. One problem with current antibodies that have been tested as therapeutics in preclinical models, as discussed above, is that many of them target C-terminal epitopes, which are not found in some of the major truncated forms of alpha-synuclein. For example, the amino acids that are important for binding of 9E4 are asparagine 122 and tyrosine 125 (according to an alanine scan presented in patent US20140127131), and this means that this antibody cannot bind alpha-synuclein which is truncated at amino acids 119, and 122, which are some of the major truncated species in Parkinson brain tissue (Kellie et al. Sci Rep. 2014; 4:5797). The same would be the case for the antibody 274 and antibody mab47 (U.S. Pat. No. 8,632,776). Also, amino terminal antibodies would possibly not be able to bind to some of the major truncated species that lack the first amino acids of alpha-synuclein, such as alpha-synuclein truncated to amino acids 5-140. For the 9E4 antibody, one suggested mechanism of action is the prevention of truncation at amino acids 119-122 in extracellular space, as the antibody will bind to the same region where the protease that will cleave alpha-synuclein (Games et al. 2014, J Neurosci. 2014 Jul. 9; 34(28):9441-54). A similar mechanism of action could also be found with antibodies in close proximity of the site, and therefore many antibodies around this region would be expected to have this activity.
There is some support for a toxic role of the truncated alpha-synuclein species in animal models. Expression of truncated alpha-synuclein under the tyrosine-hydroxylase promoter has been shown to lead to nigrostriatal pathology, which is normally not seen in transgenic alpha-synuclein models (Tofaris et al. 2006, J Neurosci. 2006 Apr. 12; 26(15):3942-50; Wakamatsu et al. 2006, Neurobiol Aging. 2008 April; 29(4):574-85). For example, expression of amino acids 1-130 of a human alpha-synuclein protein having the A53T mutation caused embryonic loss of dopaminergic neurons in the substantia nigra pars compacta whereas expression of the full length protein did not (Wakamatsu et al. 2006, Neurobiol Aging. 2008 April; 29(4):574-85). Expression of a 120 amino acid alpha-synuclein molecule under the calcium/calmodulin-dependent protein kinase II alpha (CamKII-alpha) promoter was associated with alpha-synuclein aggregation and a progressive deficit in cortical-hippocampal memory tests including the Barnes maze and novel object recognition (Hall et al. 2015, Exp Neurol. 2015 February; 264:8-13). Also in the rat AAV model co-expression of C-terminal truncated alpha-synuclein enhanced full-length alpha-synuclein-induced pathology (Ulusoy et al. 2010, Eur J Neurosci. 2010 August; 32(3):409-22).
In this invention, antibodies (such as “GM37” and “GM285”, described in the Examples) have been generated that can bind to the toxic alpha-synuclein fragment 1-119/122 and neutralize this truncated form of alpha-synuclein. The antibodies of the invention, such as GM37 and GM285, are capable of binding to other oligomeric forms of alpha-synuclein and altering their uptake by other CNS resident cells in a manner that reduce the spreading of disease. Furthermore, the antibodies of the invention, such as GM37 and 285, were surprisingly found to be superior to prior art antibodies such as 9E4 in binding to different alpha-synuclein species in human brain, and has a surprising superior effect on clearing extracellular alpha-synuclein and normalising impaired synaptic transmission induced by the presence of abnormal alpha-synuclein in vivo. Further illustrating their therapeutic capabilities, the antibodies of the invention, such as GM37 and 285, are able to prevent the appearance of a disease related motor phenotype in a rat model for Parkinson's disease. Finally, antibodies GM37 and GM285 are able to inhibit seeding of aggregation and phosphorylation of endogenous alpha-synuclein induced by extracellular added recombinant pathological alpha-synuclein seeds in primary mouse neurons. Antibodies such as GM37 and 285 can also inhibit seeding of alpha-synuclein pathology into dopaminergic neurons in vivo using a mouse model for Parkinson's disease, further supporting the therapeutic capability of these antibodies in preventing the cell to cell propagation of pathology. Together these data strongly support the use of these novel antibodies, GM37 and GM285, as new therapeutic agents capable of modifying disease through inhibition of the mechanism by which the disease pathology spreads between the neurons Parkinson's patients.
In a further aspect of the invention is provided 3 amino acid variants of the GM37 antibody. All the variants have similar functional readouts as the parent antibody, GM37, but with improved properties for manufacturability. The variants reduce the risk of post-translational modification occurring within the binding domain of the GM37 antibody and provide some improvement in the production of the antibody. This is advantageous because large scale clinical or commercial manufacturing of antibodies is complicated and expensive, and providing a homogenous product in pharmaceutical medicaments is crucial in particular for immunoglobulins and proteins.